Mercury MerCruiser MCM 454 Mag MPI Service Manual page 365

CHARGING SYSTEM
5. If reading is between 6.0 and 7.0 volts, rotor field circuit probably is open. Remove regu-
lator and inspect for worn brushes or dirty slip rings. Replace brushes if less than 1/4
in. (6 mm) long. If brushes and slip rings are in good condition, disassemble and perform
rotor test as outlined under "Component Testing - Rotor" following.
SENSING CIRCUIT
1. Unplug RED/PURPLE lead from voltage regulator.
2. Connect positive (+) voltmeter lead to red/purple lead and negative (–) voltmeter lead
to ground terminal.
3. Voltmeter should indicate battery voltage. If battery voltage is not present, check sens-
ing circuit (red/purple lead) for loose or dirty connection or damaged wiring.
Index
Page 4C-10
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a - Excitation Wire - PURPLE
b - Sensing Wire - RED/PURPLE
c - Tie Bar
d - Voltmeter (0-20 Volts)
e - Ground
a - Output Wire - ORANGE
b - Excitation Wire - PURPLE
c - Sensing Wire - RED/PURPLE
d - Voltmeter (0-20 Volts)
e - Ground
f
d
c
a
d
a
e
b
SERVICE MANUAL NUMBER 23
g
e
b
72785
c
72786
90-861326--1 MARCH 1999